1. Field of the Invention
The present invention relates generally to a small turbofan engine, and more specifically to an inlet case for the turbofan engine which houses an electric generator.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Small gas turbine engines—under around 300 pounds of thrust—are ideal for use with small unmanned aero vehicles (UAV) because of their high efficiency and light weight compared to other types of power plants such as an internal combustion engine. A small turbofan engine would have an inlet case with a row of guide vanes to direct the inlet air flow into the fan and compressor of the engine. Typical of these small turbofan engines is the use of an electric generator carried within the inlet case, since this location is ideal in that the nose cone can store the generator and the nose cone is usually empty space.
In the prior art, the inlet case is made of either a metallic material such as aluminum, steel and titanium, or a plastic material. Both of these variations of the inlet case have major drawbacks. The electric generator creates allot of heat from operation. A metallic inlet case will be a good conductor of heat (compared to the all plastic inlet case) to transfer the heat generated by the generator. However, the metallic inlet case would be relatively heavy and require complex machining (compared to the plastic inlet case) to form the inlet guide vanes. The cost of these metallic inlet cases would be very high compared to a plastic injection molded inlet case due mainly from the machining of the airfoils. In the plastic inlet case, the plastic material does not conduct heat very well. The plastic inlet case would be much cheaper to produce compared to the metallic inlet case and relatively lighter in weight. However, the plastic inlet case would not conduct enough of the heat generated by the electric generator to be of much use.